Studies will be performed to measure the permeability of the epidermal-dermal junction zone to pairs of: 1) uncharged macromolecular dextrans of several different molecular radii, 2) short chain fatty acids and diols of different numbers of OH groups. The goal of the project is to determine the nature of permeability barrier function in normal epidermis, and the extent of possible abnormalities in psoriasis, chronic solar injury, pre-cancer of skin, and diabetes mellitus. The studies will employ suction-induced blisters as in vivo diffusion chambers. A pair of substances, one labelled with 3H, the other with 14C, will be placed in each blister and the amounts of each absorbed noted. The ratio of the amounts absorbed should then provide a quantitative though indirect reflection of the permeability of the basal zone and form the basis for comparisons between disease states.